The Bottom Line: There are a variety of weak layers throughout the snowpack. The weak persistent layers closer to the top of the snowpack could provide feedback, unlike the deeper persistent layers. 

Terrain management continues to be critical! Be prepared for an avalanche that could step down to deeper instabilities, creating a slide that could break very wide, and take out all the “safe” zones on a slope. Be extra careful not to group up in places that an avalanche can reach. Be diligent and patient, practice good group management, communication and decision making. Do not ski/ride on the same slope as another group. Travel one at a time or with enough spacing so that only one person is exposed to an avalanche path at any one time. 

Buried Surface Hoar Layers:

• Jan 25th melt freeze crust is about a foot deep (with recent winds and snow, there is a lot of variability on depth of this widespread layer) sitting on top of it are near surface facets, and buried surface hoar from Feb 1-4.
• January 10th surface hoar is now buried about 2-4 feet deep. It was very active during last week’s storm cycle. Reports of remote-triggered activity on this layer Jan 27-28.
• The Dec 31 surface hoar layer is present in the Transitional and Pass zones, about 4ft deep. This layer has been active in pits, and caused some natural avalanches in early January
• Buried SH layers are tricky — they’re hard to find, and may only exist in wind-protected areas. But anywhere they are present you should be highly suspicious of that slope. It would be best to avoid wind-protected pockets that may be harboring this dangerous weak layer. Make continual assessments on test slopes and with stability tests.

Photo taken on Jan 12 of Surface Hoar on a W aspect near treeline in the Haines Pass.

Deep weak layers under strong layers are persistent in the transitional zone. A wide safety margin is necessary. This setup could produce avalanches that break wider than expected, and are most likely to be triggered from shallow trigger points like rocks or small trees or a smaller slide that steps down to these lower instabilities.  You could ride the same slope numerous times until that right spot produces a large destructive slide.

Old Melt Layers and Crusts:

• A buried persistent weak layer about 7+ feet deep (The “Big Warmup” Layer, Formed Nov 17th) is still a concern. Numerous natural avalanches observed 1/27 likely on this layer.
• A wide safety margin is necessary. This setup could produce avalanches that break wider than expected, and are most likely to be triggered from shallow trigger points like rocks or small trees. You could ride the same slope numerous times until that right spot produces a large destructive slide.

“Big Warmup” facet layer in the Transitional Zone at 2500ft on Jan 2 with test results ECTP18 that demonstrated propagation potential on this layer.

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Pit at Old Faithful, 2500’, East aspect on Jan 12. A 5″ thick layer of facets down 170cm. Also, observation noted faceted surface conditions.

Depth Hoar at the Ground (Above 3,000′):

• October snow followed by long cold snaps created depth hoar at the ground in most areas.
• You are most likely to human-trigger this layer from shallow spots around rocks, or trees, or have a surface avalanche step down to the ground on this layer. Any slides that break to the ground are likely to be deadly.

Photos shows 6-9mm advanced depth hoar at the ground down 180cm with ECTP 25 down 80cm on facets below a crust in the Haines Pass Zone at 4,000ft on a NE-aspect.